This invention relates to electrical connectors for connecting a stud terminal of electrical equipment to multiple branch-circuit wires. A transformer is the electrical equipment referenced below, but the invention may be useful in other applications.
Various electrical connectors are known for connecting the studs of certain transformers to branch-circuit wires. In U.S. Pat. No. 5,690,516 issued Nov. 23, 1997 to D. R. Fillinger, mention is made of two series of connectors as being sold by Eritech, Inc., of Aberdeen, N.C., i.e., type UPSO xe2x80x9cscrew-onxe2x80x9d connectors and type UPM xe2x80x9cslip-fitxe2x80x9d connectors. The ""516 patent discloses another xe2x80x9cslip-fitxe2x80x9d connector, similar to the UPM series. The UPSO connectors and the UPM connectors as well as those disclosed in the ""516 patent are all one-piece devices, as of extruded aluminum. A portion of the body of each of such connectors is an elongated conductor having transverse holes for branch-circuit wires and at each hole there is a clamping, wire-retaining screw. An additional hole of substantial diameter is provided in an end portion of the body of each such connector, for receiving an equipment stud, often a one-inch diameter screw-threaded stud.
Because the entire body of each of those connectors is a segmental length of an extrusion, its cross-section being so large as to accommodate entry of a stud, its cross-section is therefore excessive and wasteful for much if its length. Based on electrical and mechanical criteria, the cross-section of the elongated conductor portion of the connector could be much smaller than the cross-section required in the portion that is to receive the stud. However, due to the fact that the one-piece body of the connector is a segmental length of an extrusion, the cross-section of the entire body is as large as that required for its stud-receiving portion. In each of the slip-fit connectors of the UPM series and the slip-fit connectors of the ""516 patent, the stud-receiving hole is distinctly larger than the stud diameter, to meet the slip-fit requirement. Additionally, an increased wall thickness is provided at the hole that is to provide for slip-fit admission of the stud, to provide support for the required stud-clamping screw. Because the entire body of the slip-fit connectors is notably larger in cross-section than would be needed for the branch-circuit-connecting portions of those connectors alone, the extrusion that is used to form one-piece slip-fit connectors has an excessively large cross-section all along most of its length.
The stud-receiving hole of UPM connectors has threads matching the pitch of the stud. It is noted in the ""516 patent that, even though one or more clamping screw(s) is (are) provided at one side of the stud-receiving oversize hole in UPM slip-fit connectors, the stud may shift side-to-side despite being gripped, thereby developing instability of the stud-to-connector electrical contact. A smaller-diameter portion of a threaded hole is added in the ""516 patent,opposite to the stud-clamping xe2x80x9cjamxe2x80x9d screw, intersecting the large-diameter slip-fit hole, for blocking the stud against side-to-side shifting in the oversize hole. Adopting terminology of the ""516 patent, the jam screw is xe2x80x9cabovexe2x80x9d the aligned xe2x80x9ccentersxe2x80x9d of the large-diameter slip-fit hole and the smaller-diameter hole portion.
This invention provides a variety of novel slip-fit electrical connectors, each connector comprising first and second main components (disregarding clamping screws). For its entire length, the cross-section of the first component is an elongated conductor whose cross-section can be limited to that which is appropriate to provide for the composite branch-circuit currents and mechanical retention of the branch circuit-wires. An additional portion of the elongated conductor provides a contact area or areas for a terminal stud or for a selected, stud of either of two different diameters. That additional portion of the elongated conductor is freely exposed and accessible for machining operations that may be desirable. A second component of the novel connector is a clamp for gripping a terminal stud securely against said additional portion of the first component. Advantageously, segmental lengths of respective extrusions are used as the two components of the connector. The cross-section of each component of the novel connector can be limited to that which is essential for its own respective functions. Thus, the cross-section of the elongated branch-circuit-connection portion of the connector is not burdened, as in known one-component connectors, with material entailed in providing a stud-receiving hole.
In the following detailed descriptions and in the claims, the terminology has self-evident meanings. However, the clamp cooperates with a portion of the conductor that might be considered as having four xe2x80x9csidesxe2x80x9d. The walls of the clamp grip a portion of the conductor that has two mutually opposite xe2x80x9csidesxe2x80x9d or xe2x80x9cside surfacesxe2x80x9d. The conductor also has top or bottom surfaces contacted by a stud or studs or other electrical terminal, such surfaces being called xe2x80x9clateral surfacesxe2x80x9d hereinafter.
Modifications of a preferred embodiment of the invention reveal further aspects of the invention. In the modifications, the elongated conductor component of the novel connector has shaped contact surfaces that conform selectively to terminal studs of two different diameters. In one embodiment, one lateral surface of an end portion of the elongated connector is shaped to provide proper contact areas for studs of different diameters. One relatively short length of clamping screw in the clamp is used for establishing stud-to-connector connection for a stud of one diameter and that screw is equally serviceable with a stud of a different diameter. One length of clamping screw serves with two different diameters of studs because the clamp is selectively mountable in different positions to adapt the connector to the different stud diameters. In another modification, studs of different diameters engage contact areas on respectively opposite lateral surfaces of the additional portion of the elongated conductor. The clamp can be selectively positioned to accommodate the selective positioning of the stud at the contact areas on different lateral surfaces.
In its distinctive novel form, the clamp is a xe2x80x9cUxe2x80x9d-shaped device having side walls and a wall-connecting bridge that bears a clamping screw or screws. The clamp acts, with the contact portion of the elongated conductor, to provide a slip-fit passage that receives the terminal stud. When a stud is in place in the stud-receiving passage, the clamping screw(s) may be tightened against the stud. Notably, the side walls of the clamp and the side surfaces of the elongated conductor which confront the clamp""s side walls have mutually interlocking formations that arrest the clamp against shifting while clamping thrust is being developed by the clamping screw(s). In the embodiments of the invention shown in the accompanying drawings, the interlocking formations include projections, which may be called rails, extending from the inner surfaces of the clamp""s side walls. In the form shown, the rails on the clamps and grooves in the elongated conductor have a dove-tail cross-section. Those interlocking formations arrest the clamp against shifting during tightening of the clamping screw or screws against a terminal stud; those formations also act in preventing the clamp""s walls from spreading farther apart. By making the elongated conductor and the clamp as segmental lengths of extrusions, interlocking formations which are rails and grooves are provided at no expense for machining, and without limiting the shapes of their cross-sections. The inner surfaces of the clamp walls where those walls provide part of the slip-fit passage that receives a stud can also be shaped variously in the extrusion process, as may be desired.
The two-component form of the connector is economical in that each component is made of extruded stock whose cross-section can be made no larger than is needed for that component alone. The novel connector enables use of an extrusion for the elongated conductor whose cross-section can be much smaller than the extrusion that would be needed for the body of a one-piece connector. In its preferred embodiments, the clamp acts with the elongated conductor so as to form a stud-receiving passage for admitting either the large-diameter stud or the smaller-diameter stud, e.g., a stud of one-inch diameter or a stud of ⅝-inch diameter.
The stud-engaging contact surfaces on a lateral surface or surfaces of the elongated conductor bear(s) segments of screw threads that match the pitch and diameter of the gripped terminal stud, for arresting the connector against being pulled off the stud. A clamping screw or screws at one side of the stud drive(s) the stud into stable contact, mechanically and electrically with the selected contact area of the elongated conductor.
Illustrative embodiments of the invention described below, and shown in the accompanying drawings, represent presently preferred forms of the novel connectors. Those skilled in the art will readily devise variations and adaptations of the novel features as improvements of other electrical connectors. In modified forms, advantageous portions of the connector might be omitted together with their functions, retaining other novel features. The appended claims should be construed broadly, to encompass those variations and adaptations.